1. Field of the Invention
The present invention relates to a communication device and a method used in a wireless communication system, and more particularly, to a communication device and method of handling a Non Access Stratum procedure in a wireless communication system.
2. Description of the Prior Art
A user equipment (UE) is not allowed to transmit an Evolved Packet System (EPS) session management (SM) (ESM) request message (e.g., “PDN CONNECTIVITY REQUEST” message) by using an international mobile subscriber identity (IMSI) for an access point name (APN) if a timer is running or a Universal Mobile Telecommunications System (UMTS) subscriber identity module (USIM) is removed, when receiving an ESM cause value (e.g., #26: insufficient resources) for the APN. In addition, a UE does not transmit (e.g., initiate) another EPS mobility management (MM) (EMM) request message by using an IMSI, when an EMM request message transmitted by the UE by using the IMSI is rejected with an EMM cause value (e.g., #22: congestion). However, the operation to be performed by the UE is unknown, when the IMSI in the USIM is changed via data download, a USAT application or “REFRESH” command.
In addition, a network may transmit a NAS reject message with a cause value (e.g., #7: EPS services not allowed, #11: Public land mobile network (PLMN) not allowed, #12: Tracking area not allowed, #13: Roaming not allowed in this tracking area, #14: EPS services not allowed in this PLMN or #15: No suitable cells in tracking area) to a UE, after receiving a NAS request message transmitted from a UE by using an IMSI. Then, the UE is not allowed to transmit another NAS request message to get services in a cell, a location area, a tracking area or a PLMN where the UE receives the cause value. However, the operation to be performed by the UE when the IMSI in the USIM is changed via data download, a USAT application or “REFRESH” command is unknown, after receiving the NAS reject message with the cause value related to the IMSI.
Thus, how to handle a NAS procedure is an important problem to be solved.